DESCRIPTION: Virally-induced apoptosis is most likely important for many viruses in their pathogenesis, however viral and cellular factors mediating apoptosis are poorly understood. The long-term objective of Dr. Beth Levine s research is to understand the mechanisms by which enveloped viruses induce apoptosis. Here, she proposes to use Sindbis virus (SIN), the prototype alphavirus, to investigate virally-induced apoptosis in several mammalian cell lines and in mouse brains, to elucidate the molecular mechanism of apoptosis and to address the role of apoptosis in SIN-induced encephalitis. Her preliminary data demonstrates that the SIN E2 envelope glycoprotein induces apoptosis and that SIN-induced apoptosis can be blocked by a genetic inhibitor of cellular ICE-like cysteine protease activity. Her specific aims are to identify viral and cellular factors that mediate SIN-induced apoptosis. She will test the hypothesis that the SIN E2 transmembrane domain (TMD) acts in the endoplasmic reticulum to initiate apoptosis by: 1) identifying the death domain in SIN E2, and 2) defining the role of the SIN E2 TMD in cell death during wild-type virus infection and in the pathogenesis of fatal encephalitis. She will test the hypothesis that cellular ICE-like cysteine proteases mediate SIN-induced apoptosis by: 1) using cysteine protease inhibitors, 2) monitoring the activity of ICE-like cysteine proteases in infected cells, and 3) monitoring the interaction between ICE-like cysteine proteases and the product of the anti-apoptotic gene, bcl-xL. Finally, she will use the yeast two hybrid system to identify gene products in the brain that interact with the anti-apoptotic gene product crmA.